Look at these, I found 'em on google :)
http://www.infinite0.com/wp/wp-content/uploads/2008/03/this-sign-has-sharp-edges.jpg
http://listverse.com/wp-content/uploads/2007/10/funny-sign1-tm.jpg
http://www.mentalbreakdown.com/m_pictures/thumbs/funny-sign-boards_49.jpg
http://static.flickr.com/62/214542286_707b5b681c.jpg
http://thefeck.com/wp-content/uploads/2007/09/funny-sign-halo.jpg
http://funnysigns.kitt.net/uploaded_images/funny_sign_08-786248.jpg
http://www.funnypicturefunnyphoto.com/funny-picture-photo-funny-sign-pigeon-AMagill-pic.jpg
http://www.flixya.com/content_photos/files/xnepali11933.jpg
http://paulfite.files.wordpress.com/2008/01/funny-traffic-sign.jpg
http://www.deadgehog.com/wp-content/uploads/2007/04/31105-funny_sign_no_target_practice.jpg
http://www.guy-sports.com/fun_pictures/no_swimming.jpg
http://media.funny.co.uk/files/4009.jpg
http://www.guy-sports.com/fun_pictures/nosigns.jpg
http://eightsolid.com/wp-content/uploads/2007/10/which-way-can-i-go.jpg
http://humoursenseupgrade.com/uploads/posts/2008-03/1205940643_funny-sign-for-bananas-curved-yellow.jpg
And probably my favorite...
http://sunnythomas.files.wordpress.com/2008/05/funnysign3.jpg
